Lhasa terrane

[3] The two blocks have lithology and detrital zircon ages similar to the Qiangtang terrane and to Tethyan strata in the Himalaya, which suggests these areas were nearby in Gondwana.

[4] The South Lhasa terrane appears to have evolved as part of Australia in the late Precambrian and early Paleozoic.

In the Middle Paleozoic around 360 Ma the Lhasa and Qiangtang terranes again experienced magmatism, apparently due to the subduction of the Paleo-Tethys Ocean.

[2] The Paleo-Tethys Ocean that separated the North and South Lhasa terranes closed, and around 260 Ma in the Late Permian an HP metamorphic belt formed between the two blocks.

[2] The Tibetan Plateau was formed from a number of continental terranes that rifted from northern Gondwana in the Paleozoic and Mesozoic, moved northward and accreted to southern Asia.

In some parts of the foreland basin the north-dipping subduction of the Neotethyan oceanic crust below the Lhasa terrane caused volcanism.

The Takena formation developed in the Late Cretaceous in the foreland basin to the north of the Gangdese magmatic arc, and consists of marine limestone overlaid by fluvial red beds.

[8] Outcropped folds in the Takena formation between Lhasa and Yangbajain are upright or lean slightly to the north or south, and indicate 30% to 50% shortening in the Late Cretaceous before the Indian collision.

[12] The results of seismic reflection profiling, reported in 1998, indicate that there may be a midcrustal partial-melt zone under the length of the Yangbajain-Damxung graben starting at a depth of 12 to 18 kilometres (7.5 to 11.2 mi).

They neither support nor rule out underthrusting or fluid injection of the Indian continental crust below the Lhasa terrane.

The formation is unconformably underlain by Cretaceous sedimentary sequences more than 3,000 metres (9,800 ft) thick, which are strongly folded.

[2] Sedimentary strata from the Palaeozoic are mainly Carboniferous sandstone, metasandstone, shale and phyllite, and lesser Ordovician, Silurian and Permian limestone.

Rocks from the Triassic include inter-bedded limestone and basaltic volcanic units, most common along the terrane's southern margin.

Tectonic units of the Himalaya. Green is the Indus-Yarlung suture zone. Red is the Transhimalaya . Lhasa terrane and Lhasa city in the eastern part of Transhimalaya (Red).
Lhasa terrane approach to Qiangtang terrane
More detailed view of the tectonic evolution of the Bangong suture zone
India-Eurasia collision 70-0 Ma